Ask an Acoustic Engineer (me)

[Ge0]

Tell me about it. In the end though I think most of these fall into a few categories and the manufacturers are just using marketing tactics to make it seem like their product is different or better. We’ve got class A, class B, Class AB, Class D (T is basically chip based D) and Class G and H and a combination of those two.

WAYYYYY back in the day I used to do side jobs for Stillwater Designs (Kicker), Soundstream, and Directed Electronics. When my kids were born my primary career started to take off. I needed to drop my amplifier design and repair hobby + partial ownership of my car audio shop to focus on stable work.

A few years later I hired this kid just a few years out of college to help with automotive electronics design. I changed jobs a few times and brought him with me each time. We both enjoyed screwing around with car audio and did this together as a hobby. Then one day I was offered a management job at Harman International's car audio division. I took him with me again. However, my past employer offered me a hefty raise and promotion to stay with them. They treated me well and are one of the worlds largest suppliers of automotive electronics. I decided to stay even though working professionally in audio would be fun. I never started work at Harman but my friend did. He is now chief design engineer behind their car amplifier division. The guy who is now manager of their applications / calibration department (tuning) is also a friend and used to be a member in our local car audio club. We still keep in close touch. I enjoy hearing about some of the advanced designs they have in the pipeline. That, and if I had a car with a Harman system (Jeep Grand Cherokee) I had full access to their lab and equipment needed to tune subtle changes.

To make a long story short. Everything has gone to class D with class H type power supplies. Is that class DH or HD? Who knows. Harman calls it xAF and it is not tied to a specific hardware but a suit of hardware options.

Ge0

[Ge0]

Question that someone might be able to answer on the constant power amps,
On a 4 channel amp, if channels 3 and 4 are 2ohms and 1 and 2 are 4 ohms, when the amp detects 2 ohms on channels 3 and 4, does it then only adjust those channels for 2 ohms or does it also adjust channels 1 and 2?

Just curious about that. I am assuming it only limits channels 3 and 4.

JD, not really sure what you are asking...

Ge0

[Jdunk54nl]

JD, not really sure what you are asking...

Ge0

if an amp detects a 2 ohm load and is one of the ones that is 100w at 4 ohms or 2 ohms, when it adjusts (based on manville smiths description of the RIPS) to a 2 ohm load, so drops voltage but increases amps, does the entire amp adjust or just those specific channels or pairs of channels. Manville said the amp limits itself to a 2 ohm load until the next power cycle, I just wasn’t sure if all channels are then limited in voltage to a 2 ohm load or if just those specific channels.

[Justin Zazzi]

@justin zazzi
I read a great discussion a few posts back and wanted to revise the topic of Loud Speaker Design and innovation.
Just curious on your thoughts/opinions on why we haven't seen anything like the phoenix gold cyclone or CV Strokers in today's car audio? I don't know what the PG performance was but CV did really well with that design.

GeoLemon knocks it out of the park with a great reply to your question. I'm quoting one spot:

I can tell you from my experience with the Cyclone, that it is good for about 40hz and down (way down), but basically then you need another more traditional subwoofer to pick up the 40hz and up to wherever your midbasses really pick up. It was also very expensive, to not do everything that a subwoofer of today can do. And the real advantage was displacement - this was before "high excursion" subs really existed. I'd have to find the specs again, but this was before subs like the W7 or XBL^2 existed, so they were advertising the Cyclone had 3x the displacement of a standard 12"... which is about what a W7 does, or a CSX-12, and even a W7 is less expensive.

If I had to guess, I would say there is less need for really creative bass drivers today because the traditional design has matured a lot and there is plenty of bass available for a reasonable price now. I feel there is still a niche for ultra-low-frequency drivers like the Eminent Technology rotary woofer since getting tons of bass below 30hz is still a challenge especially if you don't have much room to work with. This one seems best suited for an infinite-baffle setup in a house playing into the attic or the basement though.

[Justin Zazzi]

if an amp detects a 2 ohm load and is one of the ones that is 100w at 4 ohms or 2 ohms, when it adjusts (based on manville smiths description of the RIPS) to a 2 ohm load, so drops voltage but increases amps, does the entire amp adjust or just those specific channels or pairs of channels. Manville said the amp limits itself to a 2 ohm load until the next power cycle, I just wasn’t sure if all channels are then limited in voltage to a 2 ohm load or if just those specific channels.

If the mechanism is to lower the rail voltage like I think RIPS does, then I imagine it would affect all channels since they usually share one set of rails.

If the mechanism is something else, then .... maybe?

[Cutaway]

This one seems best suited for an infinite-baffle setup in a house playing into the attic or the basement though.

That thing is fantastic looking and would be a great conversation piece during a boring gathering ...

[Justin Zazzi]

That thing is fantastic looking and would be a great conversation piece during a boring gathering ...

I want to make one so bad it hurts!

[Ge0]

GeoLemon knocks it out of the park with a great reply to your question. I'm quoting one spot:



If I had to guess, I would say there is less need for really creative bass drivers today because the traditional design has matured a lot and there is plenty of bass available for a reasonable price now. I feel there is still a niche for ultra-low-frequency drivers like the Eminent Technology rotary woofer since getting tons of bass below 30hz is still a challenge especially if you don't have much room to work with. This one seems best suited for an infinite-baffle setup in a house playing into the attic or the basement though.

Speaking of alternative subwoofer designs. Have ever happened to that tech where the subwoofer driver was a cylinder with a number of diaphragms inside? It was an odd shaped sub to fit into a car. But, it was a very interesting tech.

I did my searching using google. However, after a few thousand irrelevant advertiser hits I decided to give up.

Ge0

[Justin Zazzi]

Speaking of alternative subwoofer designs. Have ever happened to that tech where the subwoofer driver was a cylinder with a number of diaphragms inside? It was an odd shaped sub to fit into a car. But, it was a very interesting tech.

I did my searching using google. However, after a few thousand irrelevant advertiser hits I decided to give up.

Ge0

The Tymphany LAT (linear array transducer)?

I got to play with those recently. Kinda neat but outrageously heavy for what they were.

[dgage]

How deep and loud does the rotary subwoofer play? My 24s are flat to 7 Hz in-room at reference level. In one room I measured with the 24 placed in the corner, it was flat to 6 Hz. With conventional designs that capable, I agree it doesn’t make a lot of sense for these exotic designs that may not work as well or take a closet to work (rotary sub).